Such a system is known, for example, from DE 10 2010 060 914 A1. In order to position one or more medical referencing units on a patient's body, it is necessary at the start of a navigationally assisted operation first to record landmarks on the patient's body, for example by navigationally assisted palpation of characteristic points. Moreover, if image data of the patient's anatomy exist before the intervention, it is difficult for these image data to be brought into accordance with landmarks or characteristic points on the patient's body that have been determined in a navigationally assisted manner. In particular, this takes up a great deal of time at the start of a surgical intervention and is therefore associated with considerable cost.
By the term “surgical marker element” as used in the present patent application, it is meant to include in particular a defined reference point, for example in the form of a defined depression whose position on the carrier element is known. Such a reference point may, for example, be palpated with a navigated palpation instrument. The reference point can thereby be assigned its position in space by determining the position of the palpation instrument in space. If a bone has fixed thereto a further referencing unit comprising at least one, preferably three, surgical marker elements, then the position of the defined reference point with respect to the further referencing unit is also known so that even when the bone with the carrier element thereon is moved, a position of the defined reference point is capable of being determined at any time via the navigation system by determining the location and orientation of the further referencing unit.